The relationship between structure and function of molecules is a fundamental issue in the study of biological and other chemistry-based systems. Structure-function relationships are important in understanding, for example, the function of enzymes, cellular communication, and cellular control and feedback mechanisms. Certain macromolecules are known to interact and bind to other molecules having a specific three-dimensional spatial and electronic distribution. Any macromolecule having such specificity can be considered a receptor, whether the macromolecule is an enzyme, a protein, a glycoprotein, an antibody, or an oligonucleotide sequence of DNA, RNA or the like. The various molecules which bind to receptors are known as ligands.
A common way to generate such ligands is to synthesize molecules in a stepwise fashion on solid phase resins. Since the introduction of solid phase synthesis methods for peptides, oligonucleotides and small organic molecules, new methods employing solid phase strategies have been developed that are capable of generating thousands, and in some cases even millions, of individual molecules using automated or manual techniques. These synthesis strategies, which generate families or libraries of molecules, are generally referred to as "combinatorial chemistry" or "combinatorial synthesis" strategies. In the pharmacuetical industry these families or libraries of molecules are often formatted into 96 well plates. This formatting provides a convenient method to screen these molecules to identify novel ligands for biological receptors.
To aid in the generation of combinatorial chemical libraries, scientific instruments have been produced which automatically perform many or all of the chemical steps required to generate such libraries. An example of an automated combinatorial chemical library synthesizer is described in PCT Patent Application No. WO 97/14041, published Apr. 17, 1997, assigned to the assignee of the present invention, and incorporated herein in its entirety by reference. Another example of an automated combinatorial chemical library synthesizer is the Model 396 MPS fully automated multiple peptide synthesizer, manufactured by Advanced ChemTech, Inc. ("ACT") of Louisville, Ky. A further example of an automated combinatorial chemical library synthesizer is described in U.S. Pat. No. 5,609,826, entitled "METHODS AND APPARATUS FOR THE GENERATION OF CHEMICAL LIBRARIES," issued Mar. 11, 1997, assigned to the assignee of the present invention, and incorporated herein in its entirety by reference.
In such automated chemical library synthesizers, many different molecules are synthesized simultaneously on solid supports, with a different molecule or set of molecules being synthesized in each reaction chamber. One set of reagents is added to the solid support before the addition of the next successive set of reagents is added. Thus, each growing molecule or set of molecules is synthesized in a stepwise fashion via the addition of sets of input reagents into each reaction chamber.
As is known to those skilled in the art, the process of combinatorial synthesis not only requires the introduction of a series of reagents, but also requires washing, deblocking, capping, and other reaction steps as well. These steps must be performed regardless of the sequence in which the various reagent sets are introduced into the reaction chambers.
In some automated combinatorial chemical library synthesizers, which incorporate pipetting workstations such as the TECAN 5032 (manufactured by TECAN AG, Feldbachstrasse 80, CH-8634 Hombrechtiken, Switzerland), only one or two pipetting needles can be used to introduce the reagents or solvents used in the washing, deblocking, capping, or other commonly performed steps. Since these steps can be performed simultaneously in all of the reaction chambers, the use of only one or two pipetting needles to introduce the appropriate reagents or solvents creates a significant increase in the length of time needed to synthesize a combinatorial chemical library.
Another limiting factor in the time to produce a combinatorial chemical library is the use of an immovable reaction block installed on the operating deck of a pipetting work station. If all the procedural steps for synthesizing a chemical library must take place while the reaction block is located on the operating deck of a pipetting work station, the work station is fully occupied for the duration of the chemical synthesis. This duration may encompass hours or even days for a reaction sequence to be completed. On the other hand, the use of a movable reaction block (such as employed by Cargill and Maiefski in U.S. Pat. No. 5,609,826) allows one to employ a variety of pipetting work stations.
Yet another limiting factor in the time to produce a combinatorial chemical library is the use of a non-standard format reaction block. The use of a reaction block with 96 chambers, which allows one to synthesize combinatorial chemical libraries on 96-well microtiter plate format (with the wells on 9 mm centers), reduces the time involved in pipetting libraries into a standard 96-well format after synthesis. Thus, these libraries can be screened directly against a variety of receptors, without reformatting. For an example of such a reaction block see Cargill and Maiefski in U.S. Pat. No. 5,609,826.
Each pipetting work station may be uniquely tailored to a specific task required in the chemical synthesis (see Cargill and Maiefski in U.S. Pat. No. 5,609,826). The function of each pipetting work station may be to deliver individual reagents or sets of reagents to specific locations in a reaction block. Alternatively, the function of a pipetting work station may be to deliver an individual reagent or set of reagents to all locations of the reaction block. The function of such work stations may be best tailored to a specific set of pipetting tasks. As is known to those skilled in the art, many chemical steps that require washing, deblocking, capping, etc. are best performed simultaneously, or in other words, in parallel, in a reaction block. Thus the pipetting or delivery of washing solvents, deblocking and capping reagents, or other reagents common to all locations in the reaction block is also best performed in parallel.
The wash station described in WO 97/14041 provides a significantly improved automated wash station that has an array of 96 pipetting needles that simultaneously introduce reagents or solvents into the 96 reaction chambers in the reaction blocks. Accordingly, a synthesizing step of washing, deblocking, capping, or the like of multiple samples is done in parallel, thereby reducing the time and cost of generating a combinatorial chemical library. The synthesizing process, however, still includes time-consuming steps. For example, different reaction blocks having different samples therein often require the use of different solvents during a washing step. Furthermore, changing between solvents for washing, or changing between reagents for deblocking, for example, also includes time-consuming steps. Changing between solvents and recalibrating the wash station to provide the appropriate amount of a selected solvent for each sample can be a difficult and time-consuming process.
Other difficulties experienced by the conventional wash stations include accurately distributing a selected amount of solvent or reagent to all of the needles for simultaneous distribution into the reaction chambers. Failure to use accurate amounts of the solvent or reagent can provide inaccurate results, compromise the synthesizing process, and jeopardize the reliability of the chemical library. Such difficulties are magnified when trying to distribute the selected solvent or reagent to a large number of pipetting needles, such as an array of ninety-six needles.
A further difficulty experienced in synthesizing processes is that the same wash station typically uses a variety of halogenated and non-halogenated solvents. Disposal of the halogenated solvent can be a laborious and costly process, because disposal of the halogenated solvents must be carefully controlled for legal and environmental reasons. Disposal of the non-halogenated solvents, on the other hand, is less rigorous. Accordingly, the waste solvents are separated between halogenated and non-halogenated solvents. The separation process, however, has been a difficult process to effectively perform efficiently and inexpensively. Therefore, there remains a need in the art for an apparatus and method for quickly and efficiently performing certain reaction steps (such as washing, deblocking, capping, etc.) simultaneously and for managing the waste products (such as halogenated and non-halogenated solvents) resulting from the reaction steps.